How to wire a VFD ? What things and accessories are required for good hook up of VFD

[danishdeshmuk]

How to wire a VFD ? What things and accessories are required for good hook up of VFD ?


1) First Use a Three Phase Breaker for the input of VFD.
2) Connect the output of this breaker to a EMI Filter.
3) Then connect to R, S & T of the VFD
4) Connect Braking Resistors for frequent stops and starts of VFD
5) Connect the Output U , V & W of the VFD directly to the motor ??? OR connect the Output U , V & W of the VFD to a 3 phase contactor ? Also if use 3 phase contactor , should use an Overload also ?


6) And then from the contactor to the motor terminal .


Is the above method for hooking up VFD right ?


Also, should wire the fan (cooling fan) of the motor with external supply with a different breaker ? So that if motor runs on low speeds the fan always working with full rated rpms and hence external blower or cooling fan won't be used in this way ?


thanks a lot in advance

 

[kwired]

IMO there is way much more information involved to come up with a SOP for installing VFD's, and instead of a small punch list, you could have a 100+ page book.

When it comes to optional accessories, the application, or maybe the cost of drive or motor may come into consideration as to what value the accessory really is as opposed to just replacing the drive or motor should it fail. External overloads are typically not necessary with most drives. Fuses vs breakers on the supply goes back to is the drive worth spending extra for protection? Small drives are low enough cost maybe you don't specify fuses or breakers specifically designed for a higher level of protection over "standard" fuses or breakers. IOW is is worth spending an extra $200.00 for things like specialty fuses or breakers, line reactors, etc. for a $300 drive? There are many installed without these devices and last a long time.

Braking resistors - unless set to "coast to stop" all drives will do some braking, when decelerating but just how much braking is normally expected determines the need for a breaking resistor. Design features or even whether or not the drive is oversized for the application maybe need consideration here also.

 

[petersonra]

How to wire a VFD ? What things and accessories are required for good hook up of VFD ?


1) First Use a Three Phase Breaker for the input of VFD.

Fuses work as well, and sometimes are more appropriate depending on the short circuit current available and what OCPD might be upstream.

2) Connect the output of this breaker to a EMI Filter.

This is a CE requirement. Does not really serve much purpose. This is built in to some drives, and others it is an option that has to be bought.

3) Then connect to R, S & T of the VFD
4) Connect Braking Resistors for frequent stops and starts of VFD

Brake resistors are not always used. They are application dependent. I would guess the vast majority of VFDs do not have them as they are not needed. Incidentally, some VFDs come with the brake transistor built in, and some it is an option.


5) Connect the Output U , V & W of the VFD directly to the motor ??? OR connect the Output U , V & W of the VFD to a 3 phase contactor ? Also if use 3 phase contactor , should use an Overload also ?

I would not use an output contactor. It really does not serve much of a purpose. Most modern VFDs have the motor overload protection built in. If you need some kind of e-stop on the circuit AB (and likely others) has a safety certified doo hickey that is a lot easier to use than an output contactor. It is called a "safe off" option. Many times if you use an output contactor you will need to interlock it with the drive enable circuit.


6) And then from the contactor to the motor terminal .

These days it is becoming common to use VFD cable instead of wire.

Is the above method for hooking up VFD right ?


Also, should wire the fan (cooling fan) of the motor with external supply with a different breaker ? So that if motor runs on low speeds the fan always working with full rated rpms and hence external blower or cooling fan won't be used in this way ?

External fans are not real common these days. But if you have them, they should be on a separate contactor and not the drive.

thanks a lot in advance

There is a lot more that there could be in applying VFDs. It is highly application dependent. One common issue is the need for line and load reactors, or sometimes a DC choke. Sometimes line regen is appropriate. Environmental conditions also have an impact.

 

[kwired]

There is a lot more that there could be in applying VFDs. It is highly application dependent. One common issue is the need for line and load reactors, or sometimes a DC choke.

Good choice of words.

If that were not true then I would like to think many options would be included with the drive, instead you select options as the application dictates.

 

[danishdeshmuk]

There is a lot more that there could be in applying VFDs. It is highly application dependent. One common issue is the need for line and load reactors, or sometimes a DC choke. Sometimes line regen is appropriate. Environmental conditions also have an impact.

what does it mean by CE ?

Also, tell me more about VFD cable ? And how to select the required size VFD cable for any size VFD ?

Also, would this VFD cable be used for input and output connections of the VFD for R, S , T & U , V , W i.e. from input fuses or contractor and from VFD output to motor direct ?

thanks

 

[danishdeshmuk]

IMO there is way much more information involved to come up with a SOP for installing VFD's, and instead of a small punch list, you could have a 100+ page book.

When it comes to optional accessories, the application, or maybe the cost of drive or motor may come into consideration as to what value the accessory really is as opposed to just replacing the drive or motor should it fail. External overloads are typically not necessary with most drives. Fuses vs breakers on the supply goes back to is the drive worth spending extra for protection? Small drives are low enough cost maybe you don't specify fuses or breakers specifically designed for a higher level of protection over "standard" fuses or breakers. IOW is is worth spending an extra $200.00 for things like specialty fuses or breakers, line reactors, etc. for a $300 drive? There are many installed without these devices and last a long time.

Braking resistors - unless set to "coast to stop" all drives will do some braking, when decelerating but just how much braking is normally expected determines the need for a breaking resistor. Design features or even whether or not the drive is oversized for the application maybe need consideration here also.

why do we need to use coast to stop option of the VFD ?

In which application coast to stop option is used ?

means if we enable or use coast to stop option of the VFD then we must use braking resistors otherwise we don't , right ?

thanks

 

[kwired]

why do we need to use coast to stop option of the VFD ?

In which application coast to stop option is used ?

means if we enable or use coast to stop option of the VFD then we must use braking resistors otherwise we don't , right ?

thanks

Coast to stop simply means on stop command the drive interrupts power and the motor coasts to a stop just like an across the line controlled motor does. Otherwise without coast to stop selected (which most drives have as an option I think but is never set as a default) the drive actually decelerates the load to a stop. If the application requires a lot of stopping or maybe a high inertia load is being driven, then the braking resistor is necessary to dump energy into the resistor and protect the drive from overheating. The drive can otherwise take a certain amount of breaking without use of the external resistor.

 

[petersonra]

what does it mean by CE ?

Also, tell me more about VFD cable ? And how to select the required size VFD cable for any size VFD ?

Also, would this VFD cable be used for input and output connections of the VFD for R, S , T & U , V , W i.e. from input fuses or contractor and from VFD output to motor direct ?

thanks

CE is a mark put on products going to the common market of europe that signifies the manufacturer has certified that all applicable requirements for that type of product have been met. One requirement is that VFDs have an input EMI filter.

The major cable manufacturers such as Belden and Alpha have web pages you should be able to find that will tell you all you want to know about VFD cables.

why do we need to use coast to stop option of the VFD ?

In which application coast to stop option is used ?

means if we enable or use coast to stop option of the VFD then we must use braking resistors otherwise we don't , right ?

thanks

All stuff that is application dependent.

Not using coast to stop does not mean you need to use braking resistor. They are not directly related that way.

It is possible that you might have coast to stop enabled in a system that uses brake resistors.

Some motors also have mechanical brakes that you might well have to interlock with the drive.

 

[danishdeshmuk]

CE is a mark put on products going to the common market of europe that signifies the manufacturer has certified that all applicable requirements for that type of product have been met. One requirement is that VFDs have an input EMI filter.

The major cable manufacturers such as Belden and Alpha have web pages you should be able to find that will tell you all you want to know about VFD cables.



All stuff that is application dependent.

Not using coast to stop does not mean you need to use braking resistor. They are not directly related that way.

It is possible that you might have coast to stop enabled in a system that uses brake resistors.

Some motors also have mechanical brakes that you might well have to interlock with the drive.

so it means , if (based on application) the motor stops immediately and frequently then we must use braking resistors and enable (use) coast to stop option from the vfd , right ?

Also , if there's internal EMI filter is installed (or built in EMI filter) then we dont need to use EMI filter externally , right ?

Also, if there are mechanical braking system attached to the shaft of the motor then we must enable (use) coast to stop option and also use braking resistors , right ?

thanks

 

[petersonra]

so it means , if (based on application) the motor stops immediately and frequently then we must use braking resistors and enable (use) coast to stop option from the vfd , right ?

Use of brake resistors and coast to stop are mostly not related to each other. You might well have either, both, or neither depending on the application. Brake resistors are there to bleed off stored energy that gets made into electricity by the motor (this is called regeneration sometimes) and gets fed back into the drive's DC bus. The brake transistor connects the brake resistor to the DC as needed to bleed off the excess energy as heat.

Also , if there's internal EMI filter is installed (or built in EMI filter) then we dont need to use EMI filter externally , right ?

There is no "need" for an EMI filter at all. It is an arbitrary CE requirement. You only "need" it if you are planning to put a CE label on the equipment.

Also, if there are mechanical braking system attached to the shaft of the motor then we must enable (use) coast to stop option and also use braking resistors , right ?

Also mostly unrelated. The mechanical brake is often used to keep a load in position while the motor is inactive. Think a crane application. Motor shuts off, brake engages to keep load in place. otherwise when the motor shut off gravity would make the load fall.

 

[danishdeshmuk]

Use of brake resistors and coast to stop are mostly not related to each other. You might well have either, both, or neither depending on the application. Brake resistors are there to bleed off stored energy that gets made into electricity by the motor (this is called regeneration sometimes) and gets fed back into the drive's DC bus. The brake transistor connects the brake resistor to the DC as needed to bleed off the excess energy as heat.



There is no "need" for an EMI filter at all. It is an arbitrary CE requirement. You only "need" it if you are planning to put a CE label on the equipment.


Also mostly unrelated. The mechanical brake is often used to keep a load in position while the motor is inactive. Think a crane application. Motor shuts off, brake engages to keep load in place. otherwise when the motor shut off gravity would make the load fall.

So when and where to use braking resistors ? In what applications we should use braking resistors ? Would you name some of those applications ?

When we use braking resistor then must enable/active the coast to stop parameter from the inside of vfd ? Right

thanks

 

[petersonra]

So when and where to use braking resistors ? In what applications we should use braking resistors ? Would you name some of those applications ?

When we use braking resistor then must enable/active the coast to stop parameter from the inside of vfd ? Right

thanks

Coast to stop and braking resistor have almost nothing to do with each other.

Coast to stop means that when the drive is stopped, mechanical friction and load in the driven equipment is all that stops the motor. This is not a lot different than when you use a standard motor starter. You turn off the motor starter and friction and connected loads stop the motor.

Brake resistors are used to bleed off energy from the system as a whole that are converted to electricity when the motor becomes a generator. This can happen in a lot of ways. Take an elevator. When you are going down, you have some kinetic energy built up in the system. You have to do something with that energy when you try to stop. The motor converts that energy to electricity and feeds it into the drive. It accumulates on the DC bus raising the bus voltage. The brake resistor bleeds off some of the energy by burning it off as heat.

 

[kwired]

So when and where to use braking resistors ? In what applications we should use braking resistors ? Would you name some of those applications ?

When we use braking resistor then must enable/active the coast to stop parameter from the inside of vfd ? Right

thanks

Use resistor when you have frequent stopping or even reversing. The drive will break the motor without the resistor but if done too frequently will increase heat in the drive. The resistor is simply a place for the drive to dump excess energy it receives from breaking operations.

If you set paramaters to coast to stop then there is no dynamic breaking and no energy is transferred back to the drive so no resistor is needed.

Deceleration time is what controls breaking BTW, so the faster decel time is the more quickly energy is put back into the drive. If breaking a high inertia load you may also need a breaking resistor even if you don't decel rapidly or frequently - it all depends on how much energy the drive is going to have to take back from the load.

 

[Besoeker]

Use resistor when you have frequent stopping or even reversing. The drive will break the motor without the resistor

I wouldn't want a drive that breaks motors.But some doo and I get business from it....

 

[Besoeker]

So when and where to use braking resistors ? In what applications we should use braking resistors ? Would you name some of those applications ?

Applications where the driven load has a high inertia and, I slightly disagree with others here, infrequent stopping. Paper making machines are one example where there are large drying cylinders that would take a very long time to stop without braking. To give you an idea of numbers, it can take several minutes to get up to full speed at rated torque. Conversely, since there usually isn't a lot of friction, they can take several minutes to stop with rated torque applied in reverse for braking. Without that, the stopping is tens of minutes. Lost production is costly......

But if you need frequent stopping, a regenerative input bridge may be a better option. The stored kinetic energy goes back into the supply.
We do this for machine tool drives which have a demanding dynamic performance requirement. Stopping is frequent and when the drive is stopping the machine tool isn't machining. Again, non productive time.
So we stuff the energy back into the supply and can achieve stopping times of under a second and to with +/- half a degree of position accuracy from 10,000 rpm. It's mind blowing to watch, especially for the first time - it happens in the blink of an eye. Of course such performance doesn't come cheap and is really only justified in a few applications.

 

[kwired]

Applications where the driven load has a high inertia and, I slightly disagree with others here, infrequent stopping. Paper making machines are one example where there are large drying cylinders that would take a very long time to stop without braking. To give you an idea of numbers, it can take several minutes to get up to full speed at rated torque. Conversely, since there usually isn't a lot of friction, they can take several minutes to stop with rated torque applied in reverse for braking. Without that, the stopping is tens of minutes. Lost production is costly......

But if you need frequent stopping, a regenerative input bridge may be a better option. The stored kinetic energy goes back into the supply.
We do this for machine tool drives which have a demanding dynamic performance requirement. Stopping is frequent and when the drive is stopping the machine tool isn't machining. Again, non productive time.
So we stuff the energy back into the supply and can achieve stopping times of under a second and to with +/- half a degree of position accuracy from 10,000 rpm. It's mind blowing to watch, especially for the first time - it happens in the blink of an eye. Of course such performance doesn't come cheap and is really only justified in a few applications.

Makes sense, is there a level where it maybe is not worth putting energy back into the source? Say maybe small loads with only 5 hp or less motors driving relatively low inertia loads.

 

[Besoeker]

Makes sense, is there a level where it maybe is not worth putting energy back into the source? Say maybe small loads with only 5 hp or less motors driving relatively low inertia loads.

I'm sure there is. Financially based on return on investment for the extra capital cost of the regen circuitry.

 

[danishdeshmuk]

Use resistor when you have frequent stopping or even reversing. The drive will break the motor without the resistor but if done too frequently will increase heat in the drive. The resistor is simply a place for the drive to dump excess energy it receives from breaking operations.

If you set paramaters to coast to stop then there is no dynamic breaking and no energy is transferred back to the drive so no resistor is needed.

Deceleration time is what controls breaking BTW, so the faster decel time is the more quickly energy is put back into the drive. If breaking a high inertia load you may also need a breaking resistor even if you don't decel rapidly or frequently - it all depends on how much energy the drive is going to have to take back from the load.

So for frequent stopping and frequent starting and frequent reversing use braking resistor to avoid the drive for being heated , right ?

Also use 1 thing at a time , if using coast to stop function enable/active then don't need to use braking resistors and if braking resistors are being used then no need to active/enable the coast to stop parameter , right ?

thanks

 

[petersonra]

Also use 1 thing at a time , if using coast to stop function enable/active then don't need to use braking resistors and if braking resistors are being used then no need to active/enable the coast to stop parameter , right ?

thanks

no. they are not related. you may need either, both, or neither. it is completely application dependent.

 

[kwired]

So for frequent stopping and frequent starting and frequent reversing use braking resistor to avoid the drive for being heated , right ?

Also use 1 thing at a time , if using coast to stop function enable/active then don't need to use braking resistors and if braking resistors are being used then no need to active/enable the coast to stop parameter , right ?

thanks

The drive would still govern breaking when you decelerate without stopping, or give a reverse command. Coast to stop would only apply when a stop signal was received. To reduce speed or even reverse direction would result in deceleration parameters to be controlling the deceleration and not just letting it coast.